1. Field of the Invention:
This invention relates in general to completion equipment for wells, and in particular to a running tool for setting a casing hanger in a subsea well.
2. Description of the Prior Art:
Wells of the type concerned herein have a wellhead on the subsea floor. There will be one or more strings of casing extending down into the well. The upper end of each string of casing is connected to a casing hanger. The casing hanger has a locking mechanism for locking the casing to the wellhead. Also, the casing hanger has a seal that seals the annulus between the wellhead and the casing.
The casing hanger and the string of casing are lowered into the well on a string of drill pipe that extends upward to the floating vessel, which could be several hundred feet. A running tool, located on the lower end of the drill pipe, supports the casing hanger as it is lowered into the wellhead. Once the casing hanger is locked into the wellhead, cement is pumped down the drill pipe, down the casing, and up the annulus surrounding the casing to cement the string of casing into the well.
Then, the running tool is actuated to set the seal between the casing hanger and wellhead. Once set, the running tool is disengaged from the casing hanger, and the drill string and running tool are pulled to the surface. In an alternate method, the running tool is retrieved after cementing and fluid is circulated for cleaning. Then in a subsequent trip, the running tool sets the seal.
There are various types of running tools. The means employed to set the seal include rotation and torque, weight or pressure, and hydraulic force combined with the torque. Improvements are desired. Particularly, should the running tool fail to disengage from the casing hanger, if the running tool is of a type that uses right-hand torque to set the tool, emergency disengagement would normally have to occur by rotating the tool to the left. This is difficult to do because the joints of drill pipe might unscrew.